Noise and attenuation in long-haul optical line systems result in the deterioration of the transmitted signal, both as to its amplitude as well as its shape. Consequently, one of the fundamental requirements of nodal equipment in optical networks is the capability to regenerate and reshape the optical pulses. These functions are known as P2R, for photonic regeneration and reshaping, which is a low-cost alternative to opto-electronic transponders at network nodes that do not require data access. P2R devices can be bit-rate and data-format insensitive, which is a key advantage in system design for multi-protocol transport systems, and a signal-quality monitoring methodology that is insensitive to bit-rate and data-format is essential for implementing P2R devices in optical networks.
One well-known method for implementing P2R devices uses cross phase modulation in semiconductor optical amplifier-Mach-Zehnder interferometer (SOA-MZI) photonic integrated circuits in the Indium Phosphide materials system [1]. The ability to integrate multiple active and passive elements, operating in the C- and L-band of the optical spectrum on a single chip, is a significant advantage of this device technology. Commercial P2R devices with gains of over 10 db, which operate at up to 10 GHz over the entire C-band, have been demonstrated [2]. In addition, advanced P2R device architectures capable of achieving speeds of up to 40 GHz have been demonstrated [3].
While past work has focused on demonstrating the feasibility of P2R technology, the present invention makes P2R devices system-ready. In an optical network, power variations arising out of transients or as a precursor to failure can cause signal degradations that can propagate throughout the network. In order to arrest this propagation, optical regenerators within the network must either possess a large input power dynamic range or be able to monitor input power variations to adjust the operating set points of the regenerator.